1. Field of the Invention
The present invention relates to a controller for dimming light-emitting diodes and a method for dimming light-emitting diodes, and particularly to a controller for dimming light-emitting diodes and a method for dimming light-emitting diodes that can execute a digital dimming mode or an analog dimming mode on the same pin according to a frequency of a pulse width modulation signal.
2. Description of the Prior Art
A digital dimming mode and an analog dimming mode applied to dimming light-emitting diodes have own advantages, respectively. For example, the analog dimming mode has advantages as follows: first, the analog dimming mode has better color saturation; second, power consumption of the analog dimming mode is lower, so the analog dimming mode has more flexible product design for new energy legislation (e.g. level-6); third, the analog dimming mode does not generate moiré, so the analog dimming mode is friendly to human eyes, that is, the analog dimming mode has buzz marketing; fourth, a frequency of an electromagnetic wave corresponding to the analog dimming mode falls within a range (1 Hz-30 kHz) specified by Swedish Federation of Professional Employees (TCO). In addition, the digital dimming mode also has advantages as follows: first, the digital dimming mode has better contrast; second, color temperature and color cast corresponding to the digital dimming mode are more controlled easily; third, luminance and driving current of light-emitting diodes generated according to the digital dimming mode are varied lineally.
In the prior art, because the digital dimming mode and the analog dimming mode have own advantages respectively, although a user can set a driving circuit for driving light-emitting diodes to operate the digital dimming mode or the analog dimming mode through different corresponding external signals, the driving circuit needs to have different pins to receive an external signal corresponding to the digital dimming mode or an external signal corresponding to the analog dimming mode, or modify a printed circuit board which the driving circuit is installed in accordingly, resulting in the prior art is not a good choice for the user.